熱裂解法製備RuO2-Ta2O5/Ti電極 應用於離子液體電解液;Preparation of RuO2-Ta2O5/Ti electrode for supercapacitor in ionic liquid

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Title:	熱裂解法製備RuO2-Ta2O5/Ti電極應用於離子液體電解液;Preparation of RuO2-Ta2O5/Ti electrode for supercapacitor in ionic liquid
Authors:	許凱翔;Hsu, Kai-Hsiang
Contributors:	材料科學與工程研究所
Keywords:	氧化釕;超級電容;離子液體;熱分解;Ruthenium oxide;Supercapacitor;Ionic liquid;Thermal decomposition
Date:	2019-03-13
Issue Date:	2019-04-02 14:30:34 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究以熱裂解法(Thermal decomposition method)製備RuO2-Ta2O5/Ti電極，利用鉭的高黏著性與安定性，增加RuO2電極的穩定性，並且討論熱烈解溫度以及不同的RuCl3、TaCl5配比對RuO2-Ta2O5/Ti電極的影響，其中使用的電解液為商業上所使用的0.5 M H2SO4以及PMP-TFSI、PMP-FSI、EMI-TFSI、PMP-TFSI/PC作為電解液。首先為了瞭解不同熱裂解溫度對RuO2-Ta2O5/Ti電極的影響：本實驗在250 oC、300 oC、350 oC、400 oC在空氣氣氛下進行裂解，首先我們觀察到電極在250 oC的溫度下進行裂解後電極在電解液中產生溶解的現象，表示在此溫度下裂解電極並不穩定。在提高裂解溫度過後電極已經呈現穩定不溶解的狀態，經由材料分析能夠觀察到熱裂解溫度的不同對表面形貌與元素組成並沒有太大的影響，從XRD與XPS分析中可以看出再提高裂解溫度後尖晶石相(Rutile)RuO2強度有明顯的提升，且含水氧化釕(RuO2 xH2O)含量也隨著溫度提高而降低，在電化學分析方面：由於提高溫度造成結晶度上升與結晶水的含量降低的影響，由300 OC裂解的219 F/g 降低至400 OC下所得到的33 F/g。另一方面在不同的前驅物配比影響下，在TaCl5前驅物占比越來越高時電極表面裂縫明顯增大，從XPS與XAS分析中看出前驅物配比的不同並不影響到含水氧化釕(RuO2 xH2O)的占比且經由熱裂解法製備其化合態皆為Ru4+與Ta5+的氧化價態，氧化釕的結晶度也隨著Ta2O5含量的增加而降低，在電化學方面的發現最佳的前驅物比例為Ru：Ta＝7：3。最後將RuO2電極搭配EMI-TFSI、PMP-TFSI、PMP-FSI、PMP-TFSI/PC非質子型離子液體，其循環伏安曲線皆顯示出RuO2電極在上述離子液體中皆具有明顯的擬電容效應，且電位窗與傳統的硫酸水溶液相比也得到擴展。其中以EMI-TFSI離子液體具有最佳的電化學表現其電位窗達到3.5 V電容值達到49 mF/cm2適合作為RuO2電極之電解液。 ;In this study we synthesized RuO2-Ta2O5/Ti electrode for supercapacitors by thermal decomposition method. The influence of annealing temperature and precursor effect to the pseudocapacitive behavior of electrode were investigated systematically. In first part. The result shows that the annealing temperature at 250 OC electrode is unstable in 0.5 M H2SO4 electrolyte. While decomposition temperature increase to 300, 350, 400 OC, electrodes become stable. From XRD and XPS analysis while decomposition temperature increases, crystallinity of rutile RuO2 also increases, and the amount of hydrous-RuO2(RuO2 xH2O) is decreased while the temperature increases. Furthermore, due to the increase the crystallinity of rutile RuO2 and decrease of hydrous RuO2 cause the diffusion of proton (H+) more difficult in electrodes, so the capacitance of electrode is decrease rapidly from 219 to 33 F/g. In second part. we control the ratio of Ru and Ta precursor. The result shows that while we increase the amount of Ta precursor, it makes the crack on the surface more clearly. When Ta is reach to 70 %, Ti substrate is exposed. From EDX analysis we can see that Ti signal also increase. From XPS analysis shows that the composition of RuO2 and RuO2 xH2O doesn’t change a lot. And the crystallinity of rutile RuO2 is decrease while we add more Ta in precusor. Although increasing the ratio of Ta2O5 can reduce the crystallinity of RuO2, it also reduce the capacitance (219 F/g at 70 % Ru decrease to 64 F/g)due to the Ta2O5’s low conductivity. Finally we combined RuO2 and EMI-TFSI、PMP-TFSI、PMP-FSI、PMP-TFSI/PC ionic liquid. The cyclic voltammetry curves show that the RuO2 electrode has obvious pseudo-capacitance effect in the above ionic liquid. And the potential window is also expanded compared to the conventional aqueous sulfuric acid solution. Among them, the EMI-TFSI ionic liquid has the best electrochemical performance, and its potential window reaches 3.5 V. The capacitance value reaches 49 mF/cm2, which is suitable as the electrolyte of RuO2 electrode.
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